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#ifndef STDNET_SHA1_H
#define STDNET_SHA1_H

#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif

#include <string>

#ifndef _SHA_enum_
#define _SHA_enum_
enum {
  shaSuccess = 0,
  shaNull, /* Null pointer parameter */
  shaInputTooLong, /* input data too long */
  shaStateError/* called Input after Result */
};
#endif
#define SHA1HashSize 20

////////////////////////////////////////////////////////////////////////////////

typedef struct SHA1Context {
  unsigned int Intermediate_Hash[SHA1HashSize / 4]; /* Message Digest */
  unsigned int Length_Low; /* Message length in bits */
  unsigned int Length_High; /* Message length in bits */
  /* Index into message block array */
  unsigned int Message_Block_Index;
  unsigned char Message_Block[64]; /* 512-bit message blocks */
  int Computed; /* Is the digest computed? */
  int Corrupted; /* Is the message digest corrupted? */
} SHA1Context;

////////////////////////////////////////////////////////////////////////////////
/*
* Define the SHA1 circular left shift macro
*/
#define SHA1CircularShift(bits,word) (((word) << (bits)) | ((word) >> (32-(bits))))
/* Local Function Prototyptes */
inline void SHA1PadMessage(SHA1Context*);
inline void SHA1ProcessMessageBlock(SHA1Context*);

////////////////////////////////////////////////////////////////////////////////
/*
* SHA1Reset
*
* Description:
* This function will initialize the SHA1Context in preparation
* for computing a new SHA1 message digest.
*
* Parameters:
* context: [in/out]
* The context to reset.
*
* Returns:
* sha Error Code.
*
*/
////////////////////////////////////////////////////////////////////////////////

inline int SHA1Reset(SHA1Context* context) { //初始化状态
  if (!context) {
    return shaNull;
  }
  context->Length_Low = 0;
  context->Length_High = 0;
  context->Message_Block_Index = 0;
  context->Intermediate_Hash[0] = 0x67452301;//取得的HASH结果（中间数据）
  context->Intermediate_Hash[1] = 0xEFCDAB89;
  context->Intermediate_Hash[2] = 0x98BADCFE;
  context->Intermediate_Hash[3] = 0x10325476;
  context->Intermediate_Hash[4] = 0xC3D2E1F0;
  context->Computed = 0;
  context->Corrupted = 0;
  return shaSuccess;
}

////////////////////////////////////////////////////////////////////////////////
/*
* SHA1Result
*
* Description:
* This function will return the 160-bit message digest into the
* Message_Digest array provided by the caller.
* NOTE: The first octet of hash is stored in the 0th element,
* the last octet of hash in the 19th element.
*
* Parameters:
* context: [in/out]
* The context to use to calculate the SHA-1 hash.
* Message_Digest: [out]
* Where the digest is returned.
*
* Returns:
* sha Error Code.
*
.*/
////////////////////////////////////////////////////////////////////////////////

inline int SHA1Result(SHA1Context* context, unsigned char Message_Digest[SHA1HashSize]) {
  int i;
  if (!context || !Message_Digest) {
    return shaNull;
  }
  if (context->Corrupted) {
    return context->Corrupted;
  }
  if (!context->Computed) {
    SHA1PadMessage(context);
    for (i = 0; i < 64; ++i) {
      /* message may be sensitive, clear it out */
      context->Message_Block[i] = 0;
    }
    context->Length_Low = 0; /* and clear length */
    context->Length_High = 0;
    context->Computed = 1;
  }
  for (i = 0; i < SHA1HashSize; ++i) {
    Message_Digest[i] = context->Intermediate_Hash[i >> 2]
      >> 8 * (3 - (i & 0x03));
  }
  return shaSuccess;
}

////////////////////////////////////////////////////////////////////////////////
/*
* SHA1Input
*
* Description:
* This function accepts an array of octets as the next portion
* of the message.
*
* Parameters:
* context: [in/out]
* The SHA context to update
* message_array: [in]
* An array of characters representing the next portion of
* the message.
* length: [in]
* The length of the message in message_array
*
* Returns:
* sha Error Code.
*
*/
////////////////////////////////////////////////////////////////////////////////

inline int SHA1Input(SHA1Context* context, const unsigned char* message_array, unsigned length) {
  if (!length) {
    return shaSuccess;
  }
  if (!context || !message_array) {
    return shaNull;
  }
  if (context->Computed) {
    context->Corrupted = shaStateError;
    return shaStateError;
  }
  if (context->Corrupted) {
    return context->Corrupted;
  }
  while (length-- && !context->Corrupted) {
    context->Message_Block[context->Message_Block_Index++] =
      (*message_array & 0xFF);
    context->Length_Low += 8;
    if (context->Length_Low == 0) {
      context->Length_High++;
      if (context->Length_High == 0) {
        /* Message is too long */
        context->Corrupted = 1;
      }
    }
    if (context->Message_Block_Index == 64) {
      SHA1ProcessMessageBlock(context);
    }
    message_array++;
  }
  return shaSuccess;
}

////////////////////////////////////////////////////////////////////////////////
/*
* SHA1ProcessMessageBlock
*
* Description:
* This function will process the next 512 bits of the message
* stored in the Message_Block array.
*
* Parameters:
* None.
*
* Returns:
* Nothing.
*
* Comments:
* Many of the variable names in this code, especially the
* single character names, were used because those were the
* names used in the publication.
*
*/
////////////////////////////////////////////////////////////////////////////////

inline void SHA1ProcessMessageBlock(SHA1Context* context) {
  const unsigned int K[] = { /* Constants defined in SHA-1 */
      0x5A827999,
      0x6ED9EBA1,
      0x8F1BBCDC,
      0xCA62C1D6
  };
  int t; /* Loop counter */
  unsigned int temp; /* Temporary word value */
  unsigned int W[80]; /* Word sequence */
  unsigned int A, B, C, D, E; /* Word buffers */
  /*
  * Initialize the first 16 words in the array W
  */
  for (t = 0; t < 16; t++) {
    W[t] = context->Message_Block[t * 4] << 24;
    W[t] |= context->Message_Block[t * 4 + 1] << 16;
    W[t] |= context->Message_Block[t * 4 + 2] << 8;
    W[t] |= context->Message_Block[t * 4 + 3];
  }
  for (t = 16; t < 80; t++) {
    W[t] = SHA1CircularShift(1, W[t - 3] ^ W[t - 8] ^ W[t - 14] ^ W[t - 16]);
  }
  A = context->Intermediate_Hash[0];
  B = context->Intermediate_Hash[1];
  C = context->Intermediate_Hash[2];
  D = context->Intermediate_Hash[3];
  E = context->Intermediate_Hash[4];
  for (t = 0; t < 20; t++) {
    temp = SHA1CircularShift(5, A) +
      ((B & C) | ((~B) & D)) + E + W[t] + K[0];
    E = D;
    D = C;
    C = SHA1CircularShift(30, B);
    B = A;
    A = temp;
  }
  for (t = 20; t < 40; t++) {
    temp = SHA1CircularShift(5, A) + (B ^ C ^ D) + E + W[t] + K[1];
    E = D;
    D = C;
    C = SHA1CircularShift(30, B);
    B = A;
    A = temp;
  }
  for (t = 40; t < 60; t++) {
    temp = SHA1CircularShift(5, A) +
      ((B & C) | (B & D) | (C & D)) + E + W[t] + K[2];
    E = D;
    D = C;
    C = SHA1CircularShift(30, B);
    B = A;
    A = temp;
  }
  for (t = 60; t < 80; t++) {
    temp = SHA1CircularShift(5, A) + (B ^ C ^ D) + E + W[t] + K[3];
    E = D;
    D = C;
    C = SHA1CircularShift(30, B);
    B = A;
    A = temp;
  }
  context->Intermediate_Hash[0] += A;
  context->Intermediate_Hash[1] += B;
  context->Intermediate_Hash[2] += C;
  context->Intermediate_Hash[3] += D;
  context->Intermediate_Hash[4] += E;
  context->Message_Block_Index = 0;
}

////////////////////////////////////////////////////////////////////////////////
/*
* SHA1PadMessage
*
* Description:
* According to the standard, the message must be padded to an even
* 512 bits. The first padding bit must be a ’1’. The last 64
* bits represent the length of the original message. All bits in
* between should be 0. This function will pad the message
* according to those rules by filling the Message_Block array
* accordingly. It will also call the ProcessMessageBlock function
* provided appropriately. When it returns, it can be assumed that
* the message digest has been computed.
*
* Parameters:
* context: [in/out]
* The context to pad
* ProcessMessageBlock: [in]
* The appropriate SHA*ProcessMessageBlock function
* Returns:
* Nothing.
*
*/
////////////////////////////////////////////////////////////////////////////////

inline void SHA1PadMessage(SHA1Context* context) {
  /*
  * Check to see if the current message block is too small to hold
  * the initial padding bits and length. If so, we will pad the
  * block, process it, and then continue padding into a second
  * block.
  */
  if (context->Message_Block_Index > 55) {
    context->Message_Block[context->Message_Block_Index++] = 0x80;
    while (context->Message_Block_Index < 64) {
      context->Message_Block[context->Message_Block_Index++] = 0;
    }
    SHA1ProcessMessageBlock(context);
    while (context->Message_Block_Index < 56) {
      context->Message_Block[context->Message_Block_Index++] = 0;
    }
  }
  else {
    context->Message_Block[context->Message_Block_Index++] = 0x80;
    while (context->Message_Block_Index < 56) {
      context->Message_Block[context->Message_Block_Index++] = 0;
    }
  }
  /*
  * Store the message length as the last 8 octets
  */
  context->Message_Block[56] = context->Length_High >> 24;
  context->Message_Block[57] = context->Length_High >> 16;
  context->Message_Block[58] = context->Length_High >> 8;
  context->Message_Block[59] = context->Length_High;
  context->Message_Block[60] = context->Length_Low >> 24;
  context->Message_Block[61] = context->Length_Low >> 16;
  context->Message_Block[62] = context->Length_Low >> 8;
  context->Message_Block[63] = context->Length_Low;
  SHA1ProcessMessageBlock(context);
}

////////////////////////////////////////////////////////////////////////////////

inline std::string hash_sha1(const std::string& data) {
  SHA1Context sha;
  if (SHA1Reset(&sha) != shaSuccess) {
    return "";
  }
  if (SHA1Input(&sha, (unsigned char*)data.c_str(), (int)data.size()) != shaSuccess) {
    return "";
  }
  unsigned char hash[SHA1HashSize];
  if (SHA1Result(&sha, hash) != shaSuccess) {
    return "";
  }
  return std::string((char*)hash, sizeof(hash));
}

////////////////////////////////////////////////////////////////////////////////

#endif //STDNET_SHA1_H
